It rains a lot in the Pacific Northwest. Everyone knows that. We are often accused of walking around with “webbed feet.” Funny, but only if you're a duck!
However, water in buildings isn't funny. Neither is mold. Both are facts of life, and not just in the Northwest.
Every mason in the U.S. and Canada has to deal with water infiltration –through window and door cuts, via wind-driven rain, and inherently, from the installation of the product itself. Mortar and grout contain a very high percentage of water.
Ask yourself, “Where should that water go?”
The answer is obvious – the water needs to be directed “out” of the building, not “in.” The result of water “in” a building quickly becomes obvious – mold. Once moisture has penetrated deep into a wall system through the moisture-resistant construction paper and into the exterior sheathing, the wall is “deep” wet. Airflow that exists in most wall systems is a slight draft that does not dry this condition out quickly. The wall is now in serious trouble.
Use of a rainscreen drainage plane (moisture control and weep system) is the recommended method to direct moisture out of and away from the wall. So why then do most masons, even architects, steer away from insisting upon and/or specifying a rainscreen drainage plane system? The answer, as always, is dollars and cents.
They'd rather “risk” the outcome than use “risk management” to prevent the ultimate outcome, all for the sake of a few cents per square foot. I've heard time and time again that a rainscreen drainage plane system was specified but was “value engineered” out. Why?
Again, it saved a few cents, but look at the risk. We live in a litigious society. Lawsuits are rampant and insurance costs are sky-high, or not even available. Why? Because someone opened the closet door and found a mushroom the size of Yankee Stadium in the hallway. The next steps include an attorney, investigator, and lawsuit.
A rainscreen drainage plane system separates the exterior veneer from the moisture-resistant surface of the structural back-up wall. It allows any moisture in a liquid state (water or condensation) that passes through the rainscreen to have an unobstructed pathway from a high point of the wall, where it enters, to a low point of the wall, where it exits. The water should exit the wall system quickly.
A rainscreen drainage plane system provides the first line of defense against the effects of moisture on the wall detail (see photo). It also helps protect the interior of the wall detail from variations in air pressure, wind, ultraviolet rays, and other severe weather conditions. The rainscreen drainage plane and weeps allow water that passes through the rainscreen (veneer) to travel down and out of the wall detail.
A veneer that does not stand off from the moisture-resistant surface of the structural back-up wall to create a cavity is not a true rainscreen. It's just a veneer. Technology that works as a predictable drainage plane must create a separation between the backside of a masonry veneer and the exterior surface of the moisture-resistant construction paper that is installed on the exterior sheathing of the structural back-up wall.
Are you willing to risk your reputation, livelihood, and company for a few cents per square foot of wall? I think not. Insist upon a rainscreen drainage plane system. Use “risk management” as your leverage.
Barbara Headrick, executive director of RMCA, has been promoting the use of masonry as a building system for many years. For more specific information on rainscreen systems, visitwww.mtidry.com, or call her at 206-719-0051.